MICROBIOLOGICAL AND PHYSICOCHEMICAL CHARACTERISTICS OF 'TIRAKI', A TRADITIONAL CHEESE OF TINOS ISLAND

摘要

"Tiraki" is a traditional cheese made in Tinos island from cow's milk by enzyme and acid coagulation. It has fresh and pleasant taste and rich flavour. The objective of the present work was to study the cheese-making process and the microbiological and physicochemical characteristics of the cheese throughout manufacture and storage in order to produce more consistently high quality cheese. Four batches of cheese were made at Tinos dairy factory (E.A.I) according to the traditional method. The results showed that the cheeses characterized by pH 4,38, moisture 40%, fat in dry matter 57,15% and proteins in dry matter 37,37%. The total saturated fatty acids content was 73,81% of total fatty acids, the monosaturated fatty acids 23,43% and the polysaturated fatty acids 2,75%, while cholesterol content was 126,43mg/100g of cheese. Acetaldehyde, 3-methylbutanal and acetic acid were the most abundant flavour compounds detected. Ca, Mg, and P levels were low due to their removal in the whey during drainage. Proteolysis was limited during storage of cheese at 4°C up to 90 days. Raw milk added for acid coagulation, low pH, salting and kneading of curd create conditions for the development of special microflora. Lactic acid bacteria predominated over the other microbial groups. The counts of lactic acid bacteria, both thermophilic and mesophilic rods and cocci, were above 10scfu/g. Enterococci, coliforms, micrococci and yeasts were also present at considerably high levels. During 90 days of cold storage, lactic acid bacteria remained at high levels, while mesophilic bacteria had greater viability. The counts of micrococci remained stable, yeasts populations were increased and coliforms were significantly declined, due to their sensitivity to acidic pH and low temperature. All cheeses were free of Salmonella sp. and Listeria monocytogenes. On the basis of the above findings "Tiraki" is a nutritious food. Except for the need of product standardization, high quality cheese could be produced applying strict hygiene conditions during manufacture. Cold storage can contribute towards this direction. In addition, strains selected from cheese native microflora could also be used as starters, instead of raw milk.